Using behavioral techniques spatial contrast sensitivity was measured in normal cats, dark-reared cats and cats with bilateral, central, retinal lesions. In normal animals, one-dimensional visual noise interferes with grating detection only if the noise contains energy within plus or minus 1 octave of the test spatial frequency. This result provides a psychophysical index of spatial tuning in cat vision. Cats with central retinal lesions exhibit losses in contrast sensitivity only at higher spatial frequencies, confirming the functional significance of the area centralis. Dark-reared cats show permanent losses in contrast sensitivity across the entire spatial frequency spectrum and they fail to improve in sensitivity even when temporal modulation of the pattern is introduced. This loss in visual function correlates well with changes in receptive-field properties of neurons in the lateral geniculate nucleus and visual cortex of dark-reared cats.